This invention is aimed for use in fully automatic hot beverage dispensing machines for homes, offices or so called food-service—or HoReCa—sites. The invention apparatus can also be used to dispense hot beverages from soluble products, i.e. the so-called instant drinks.
Fully automatic beverage dispensing machines, particularly the ones brewing hot drinks from ground fresh ingredients, are not yet recognised for an outstanding quality of their drinks. A manually prepared espresso by a skilled barman (barista) is still seen as a better beverage than one prepared by an automatic machine.
Steps to prepare a manual espresso have been described in several publications. These steps are: ensuring temperature of all components involved in the dispensing of the beverage is correct; weighing the amount of ground roasted coffee (e.g. 6.5 grams); coffee grinding adjusted to obtain the suitable particle size, making sure that the climatic conditions, especially relative humidity, do not change ideal grinding size, so as to have a correct brewing time (e.g. 25″ for 40 cc.) is regularly achieved; compacting the coffee inside the brewing chamber, usually attached to a handle, with the aim to achieve the right brewing time via the correct drag through the coffee cake.
There are many patents directed to using the above concepts for improving coffee quality.
EP0554650 to Cavazzuti and Annibali teaches that an ideal size of roasted coffee grind for espresso coffee is between 25 to 395 microns and preferably 195 to 240 micron.
In FR2477001 to Grossi, the brewer includes a mechanical system to have the grinder to modify the average particle size of the coffee. The magnitude of such modification is based upon the discrepancy between the brewing time effectively needed to dispense one espresso coffee and a standard brewing time (fixed at thirty seconds), considered to be the ideal brewing time.
U.S. Pat. No. 4,767,632 to Meier teaches to measure the displacement path of the compression piston and the time required to dispense a preset volume of beverage, to compare these data to stored data and to use a possible difference between these parameters as means to adjust the amount of coffee and the size of milled coffee particles when brewing subsequent beverages.
U.S. Pat. No. 5,645,230 to Marogna discloses a coffee grinding and dosing apparatus provided with means to detect ambient humidity and to accordingly adjust the grinding blade distance to provide a finer or coarser particle size.
The above solutions, however, are not sufficient because several other factors may affect the correct dispensing of a coffee.
In some cases deposits of ground coffee build up on the coffee chute placed above the brewing chamber: less coffee reaches the brewing chamber until the deposits collapse to discharge a greater amount of ground coffee in the chamber. Variable quantities of coffee in the brewing chamber may also be due to lack of precise measuring devices: such is the case when the grinder is operated for a pre-set amount of time, when volumetric chambers are fed with coffees having different particle sizes, e.g. because of wear of the grinder.
EP1306040 to Mestek, EP0486434 to Torma and other documents describe a closing piston in the brewing chamber using a “compensation spring” i.e. a mechanically resilient means to alter temporarily the internal volume of the brewing chamber. Such a solution relies on the physical properties of the spring and on the amount of coffee and pressure of water within the brewing chamber and certainly cannot give an adaptive answer to conditions dictated by other considerations such as the type of coffee to be dispensed or desired extraction yield.
The above discussed documents do not address the problems related to the type of coffee being dispensed, the volume or size of ground coffee used, or other considerations suggested by market preferences or cost-saving. It must be considered also that the concept of coffee may be differently interpreted and a coffee machine has to be an answer to the different requirements of the end users.
Moreover, in a dispensing machine using pre-filled capsules containing ground coffee, the capsules cannot undergo any further grinding of the coffee therein contained and, therefore, this parameter cannot be changed.
Therefore, there is the necessity of a brewing process and machine that can automatically compensate for the many changes of the product or the dispensing conditions in order to have a constant good coffee quality.
There is also the need of a process and a machine that carries out such compensation in real time, i.e. during the same brewing procedure.